Ultrastructural features of spermatozoa and their phylogenetic application in Zaprionus (Diptera,Drosophilidae)

The genus Zaprionus consists of approximately 60 species of drosophilids that are native to the Afrotropical region. The phylogenetic position of Zaprionus within the Drosophilidae family is still unresolved. In the present study, ultrastructural features of spermatozoa of 6 species of Zaprionus as well as the species Drosophila willistoni and Scaptodrosophila latifasciaeformis were analyzed. The ultrastructure revealed that the species have the same flagellar ultrastructure. Two mitochondrial derivatives, one larger than the other, close to the axoneme were present, primarily in D. willistoni (subgenus Sophophora). Except for Z. davidi and Z. tuberculatus, the analyzed species had paracrystalline material in both mitochondrial derivatives. Moreover, the testes showed 64 spermatozoa per bundle in all of the species. In the cluster analysis, 6 Zaprionus species were grouped closely, but there were some incongruent positions in the cladogram. The results indicated that sperm ultrastructure is an important tool for elucidating the phylogeny and taxonomy of insects.     

Influence of the antioxidants vitamin E and idebenone on retinal cell injury mediated by chemical ischemia, hypoglycemia, or oxidative stress

A role for the antioxidants vitamin E and idebenone in decreasing retinal cell injury, after metabolic inhibition induced by chemical ischemia and hypoglycemia, was investigated and compared with oxidative stress conditions. Preincubation of the antioxidants, vitamin E (20 microM) and idebenone (10 microM), effectively protected from retinal cell injury after oxidative stress or hypoglycemia, whereas the protection afforded after postincubation of both antioxidants was decreased. Delayed retinal cell damage, mediated by chemical ischemia, was attenuated at 10 or 12 h postischemia, only after exposure to the antioxidants during all the experimental procedure. An antagonist of the N-methyl-D-aspartate (NMDA) receptors, an inhibitor of nitric oxide synthase (NOS) or a blocker of L-type Ca2+ channels were ineffective in reducing cell injury induced by chemical ischemia, hypoglycemia or oxidative stress. Oxidative stress and hypoglycemia increased (about 1.2-fold) significantly the fluorescence of the probe DCFH2-DA, that is indicative of intracellular ROS formation. Free radical generation detected with the probe dihydrorhodamine 123 (DHR 123) was enhanced after oxidative stress, chemical ischemia or hypoglycemia (about 2-fold). Nevertheless, the antioxidants vitamin E or idebenone were ineffective against intracellular ROS generation. Cellular energy charge decreased greatly after chemical ischemia, was moderately affected after hypoglycemia, but no significant changes were observed after oxidative stress. Preincubation with vitamin E prevented the changes in energy charge upon 6 h posthypoglycemia. We can conclude that irreversible changes occurring during chemical ischemia mainly reflect the alterations taking place at the ischemic core, whereas hypoglycemia situations may reflect changes occurring at the penumbra area, whereby vitamin E or idebenone may help to increase cell survival, exerting a beneficial neuroprotective effect.